The present invention relates to a mechanism for applying a clamping force to a columnar member which has particular utility in machines for molding articles.
Clamping systems for molding machines typically use means to lock the tiebars in order to connect and disconnect clamping pistons to them. For example, French patent 2,411,694 illustrates a friction means for gripping the column of a three platen machine in order to connect a clamping piston to the column. The design uses a conical locking ring that is pushed into a tapered sleeve, which causes the locking ring to deflect inward and grip the column passing through its central bore. FIG. 4 of this patent shows how the locking ring has longitudinal slots cut through it to facilitate this deflection. The problem with this approach is that the locking ring must slide inside its mating tapered piece in order to be deflected. The high forces generated during this sliding action cause wear on the mating surfaces which substantially shorten the useful life of such a device. Furthermore the friction in the conical seats limits the effectiveness of the gripping action.
U.S. Pat. No. 2,691,799 illustrates a different approach. In this patent, a collet-type locking ring is used to grip a tiebar.
U.S. Pat. No. 3,183,555 to Siegel illustrates an approach using a hydraulic pressure to deflect the walls of a sleeve to grip a tiebar.
U.S. Pat. No. 4,565,517 to Brinkmann illustrates an approach using oil pressure to act on a piston having a conical seat that causes ring segments to grip a tiebar.
German Patent No. 31 44 359 illustrates an approach using a hydraulic piston to push against wedge shaped segments to grip a rod of a piston.
Despite these systems, there still remains a need for a clamping mechanism with stronger gripping action which works faster to minimize the problems with wear and which can be built at a substantial cost saving.